Rubber powder



Unite States Patent (Y 3,042,633 RUBBER rovvnnn Woodrow W. White, ()xford, Conn, assignor to United States Rubber Company, New York, N.Y., a corporation of New Jersey N Drawing. Fiied Apr. 29, 1957, Ser. No. 653,745 12 Claims. (-Cl. 260-3) This invention relates to improvements in rubber powder for incorporation in the bituminous binder used in building roads, and for other purposes.

In conventional road building practice, hot bituminous binder (asphalt or road tar) is mixed with the aggregate at a pug mill, generally in amount from 3 to 15% on the weight of the aggregate, and the mix is then transported to the paving site, or the dry aggregate is first laid on the road and the hot bituminous binder is then sprayed on the aggregate. In these operations the binder is at a temperature of 250 F. to 400 F. (generally 250 F. to 350 F.).

Rubber powders prepared directly from natural and synthetic rubber latices have been incorporated in the hot bituminous binder used with the mineral aggregate in forming paving compositions, generally in amounts to give 1 to 15 parts of rubber per 100 parts of bituminous binder. However, such rubber p wders do not flow easily and have a tendency to sinter in storage and thus make difiicult their handling and measuring and their gradual addition to the hot melt of bituminous material.. One method of attempting to overcome this difliculty has been tovulcanize the latex before producing the rubber powder. Another method has been to coprecipitate the rubber in the latex with an equal amount or more of ground inert mineral filler. These methods introduce other disadvantages. The vulcanization reduces the compatibility of the rubber with the bituminous binder. The large amount of filler increases the extraneous material which is shipped about and has a tendency to settle out when added to bulk quantities of the bituminous binder.

By the present invention, there is provided an improved rubber powder which is free-flowing and non-sintering under storage conditions and which is readily and uniformly dissolved or dispersed in hot bituminous material.

According to the present invention, the individual particles of rubber powder prepared directly from latex are coated with an aldehyde resin which imparts the freeflowing properties to the crumbs, and permits ready dissolution of the rubber in the bituminous material. Such resin coated powder may be mixed with the hot bituminous binder for the aggregate in road building generally in amount from 1 to 15 parts of rubber per 100 parts of bituminous binder. Mixtures of bituminous material and the resin coated powder in amount up to 25 parts of rubber per 100 parts of bituminous material may be used as expansion joint fillers in road construction, and as laminating adhesives in making paper to paper and paper to metal foil laminates. The rubber powders with the resin coating on the individual rubber particles may be used directly in molding and extrusion processes to give finished rubber articles.

In carrying out the present invention, the rubber latex which may be unvulcanized or vulcanized or which may contain vulcanizing ingredients, softeners, extenders or fillers, emulsified or dispersed therein, is flocculated in the conventional manner to form ready filte'rable fiocs. For example, the latex may be creamed by addition of a solution of a monovalent salt, such as sodium chloride, and then vinyl pyridines; alkyl vinyl pyridines.

fiocculated with dilute acid, such as sulfuric, hydrochloric I or acetic acid, or by dilute solutions of multivalent salts.

of strong acids, such as calcium chloride or aluminum sulfate. The addition of up to 20 parts of sodium lignate per l00 parts of rubber of the latex before flocculation 3,042,633 Patented July 3, 1962 gives flocs of reduced size. After the latex has been coagulated to a fine fiocculate, an aldehyde resin is incorporated in the aqueous medium of the slurry of the rubber fiocs and the resin is precipitated therein to form a waterinsoluble coating on the flocs. The flocs may then be dewatered as by filtering, and dried as in conventional rubber practice. The aldehyde resin may be phenol-aldehyde, resorcinol-aldehyde, urea-aldehyde, melamine-aldehyde or aniline-aldehyde resin in which the aldehyde is formaldehyde or acetaldehyde. An aqueous solution of the reatant other than the aldehyde may be added to the aqueous slurry of the rubber flocculate followed by an aqueous solution of the aldehyde or an aqueous solution of a mixture of the two may be added to the aqueous slurry. The molar ratio of reactant other than aldehyde to aldehyde is generally from about 1:0.75 to 1:2.0. The mixture of the resin reactants in aqueous acid medium of the slurry of the rubber fluocculate is agitated for a short time, e.g. from /2 to 3 hours at temperature from 50 C. to C. for formation of the water-soluble resin after which the pH is raised to 8 or above by the addition of dilute alkali. As the pH is raised, the resin which has been formed in the acid phase is precipitated and deposited on the surface of the rubber flocs giving a product which is non-tacky because the particles are coated with a brittle non-tacky resin. The resulting particles aredewatered as by filtering, and dried, giving a fine free-flowing powder. The amount of resin may be from 2 to 30% of the final coated particles with the preferred level being 10 to 16%. The dried resin coated rubber particles may be in the range from 10 to 200 mesh, and generally will be in the range y from 30 to 100 mesh. The amount of the thus prepared resin coated rubber powder that is mixed with the hot bituminous binder is that which gives from 1 to 15 parts of rubber per 100 parts of the asphalt or road tar binder, whether added as such in the pug mill with the hot aggregate and the binder, or mixed with the hot binder before introduction into the pug mill, or mixed with the hot binder before spraying on the rolled hot aggregate. As above described, the temperature of the binder in these operations is from 250 F. to 400 F. (generally 250 to 350 F.).

The latex may be a natural or synthetic rubber latex. The synthetic'rubbcr latex may be a so-called butadiene polymer synthetic rubber latex, i.e. an aqueous emulsion polymerizate of one or more butadienes-l,3, for example, butadiene-1,3, 2-methylbutadiene-l,3 (isoprene), 2- chlorobutadiene-1,3 (chloroprene), 2,3-dimethylbutadicue-1,3, piperylene, or a mixture of one or more such butadienes-lfa" with one or more other polymerizable compounds which are capable of forming rubbery co-' polymers with butadienes-1,3, for example, up to 70% a CH =C group and are copolymerizable with butadi-- cue-1,3 hydrocarbons are aryl olefines, suchv as styrene, vinyl toluene, alpha methyl styrene, chlorostyrene, dichlorostyrene, vinyl naphthalene; the alpha methylene carboxylic acids and their esters, nitriles and amides, such as acrylic acid, methyl acrylate, methyl .methacrylate; acrylonitrile, methacrylonitrile, methacrylamide; methyl vinyl ether; methyl vinyl -ketone; vinylidene chloride;

Common commercial synthetic rubber latices arelaticesof GR-S (copolymer of a major proportion of butadiene and a minor proportion of styrene), Paracril (copolymer of a major proportion of butadiene and a minor proportion .of acrylonitrile); and neoprene (polymerized chloro-Z-buta 7 210% formaldehyde.

agitation at 140-150 for one hour, after which the construction by. pouring in "melted;

. diene1, 3). Such latices may be compounded with softeners, extenders and fillers by adding emulsions or dispersions of the same to the latex before flocculation. .For example, asphalt and tar softeners and extender oils .such asheavy petroleum fractions may be added to the "latex as emulsions generally in amount up to'one-half 'of the weight of the rubber. r

The following'illustrates the invention. 7 All parts and percentages referred to herein are by weight. 144. pounds (40 pounds dry'weight) of a latex of a copolymer of 175 parts of butadiene and 125 parts of.

styrene were stabilized to'oxidation by the addition of in admixture with previously flocculated rubber latex particles onto said'flocculated rubber latex particles, said 1189 pounds (0.6 pounds dry Weight) of an aqueous emulsion of condensed diphenylamine acetone reaction product. preparediby dissolvingf0.82 pounds of sodium hydroxide A solution of sodium lignate which had been in;l0 pounds'of water and'dissolving 2.0 pounds of .lignin (Indulin A) in the solution was then added. This ''mixture was creamed .with'320 pounds (24 pounds dry weight) or a sodium chloride solution which was adjusted to 'a pH of 10' with sodium hydroxide. iFlocculation was then accomplished under. vigorous agitation, by the addition of suificient sulfuric acid tetraethylene penta mine solution (2 pounds sulfuric acid and 0.4 pounds of tetraethylene pentamine "to obtain smooth flocculation per 38-pounds of water) to reduce the pH to 2. The floc fculate was" in very fine particles. "A solution containing 3.3porinds of aniline dissolved in l.9 pounds'of sulfuric acid and 74.8 pounds of water was then added followed rubber being selected from the group consisting of natural rubber and synthetic rubber emulsion polymerizates of material selected from the group consisting of butadienes- 1,3 and mixtures of butadienes-1,3 with compounds which contain a CH =C group and are copolymerizable with butadienes-1,3. t

2. A free flowing dried resin coated rubber powder the particles of which are 1010 200 mesh size and are coated with aniline-formaldehyde resin, said resin being precipitated from asoluble state in an aqueous acid medium in admixture with previously flocculated rubber latex particles onto saidfloeculated rubber latex particles, said rubber being selected from the group consisting of natural rubber and synthetic rubber "emulsion polymerizates of material selected from the group consistingof butadienes-1,3 and mixtures of butadiezies-LS withcompounds which containa CH =C group and are copolyrneriza-' ble with butadiene's-Ll. l Y

3. A free flowing :dried. resin coated rubber powder the particles of which aIe'lO to 200 mesh size and are coated with resin selected from the group consisting of phenol-aldehyde, resorcinol-aldehyde, urea-aldehyde, melamine aldehyde and aniline-aldehyde resins in which the aldehyde is selected from the group consisting of formaldehyde and acetaldehyde, said resin being in amountfrom'2 to by weight of the coated particles and being precipitated from a soluble 'state in an aqueous acid medium in'admixture with previously flocculated rubber latex particles onto said'flocculated rubber latex particles, said rubber being selected from the group consisting of natural rubber and synthetic rubber emulsion bythe addition of l0 pounds (.4 pounds dry'weight') of 1 The mixture was then held under pH was raised to 8 using a solution of sodium hydroxide. The resin deposited on the rubber flocs. The fine flocculate was then filtered onto cheese cloth and dried over:

350 in a closed container equipped with an agitator.

I The asphalt had a penetration va ue at 77F. of 110-120 (A.S.T;M.- D5-52).' The rubber was completely disroad construction. l a

'lwenty'p'ar tsof the above resin coated rubber powder were added'to $0 parts of asphalt at 32 5* F. in an inte'rnal mixer of the'Wernerand Pfleiderer type; The asphalt had a penetration value at 77 F. of about 200 (A.S.T.M. D5,-5.2). The rubber was completely dispensedin the asphalt. giving a smooth mix in four hours.

ree pants of the fzhus prepared resin coatedrubber powder Were added to 97 parts of asphalt heated: to about polymerizates of material's'elected from'the group consisting of butadienesl,3 and mixtures of butadienes-1,3

with compounds which contain a'CH =C group and are copolymerizable with butadienes-lfi 4. A' free flowing dried resin coated rubber powder the particles of which are 10 to 200 me shsize and are coated with 'aniline-formaldehydefresin, said resin being in amount from'2 t'o' 30% by weight of the coated partieles and being'precipitated from a soluble state in an 7 :aqueous acid'medium in admixture with previously flocculated rubber latex particles onto saidfioc'cul-ated rubber latex particles, said rubber being selected from the group consisting of natural rubber and synthetic rubber emulsion polymerizatesjof'nlaterial selected from the f group consisting of butadienes-lfi rand of buta- 7 persed inthe asphaltfgiving a smooth mix in three hours;

'Such blend is useful as a binder for the aggregate in.

dienes'-l,3 with. compounds which contain a .CH C group and are copolymeriizable with butadie nes-l,3.

V 5.. The method of making free flowing resin coated rubber powder of particlesof 10 to 200 mesh sizefrom latex which comprises first flocculating'the latex and then depositing resin selected: from the group consisting of phenol-aldehyde, resorcinol-aldehyde, urea-aldehyde,

. melamine aldehyde and aniline-aldehyde resins in which Such blend useful for filling expansion joints in paving r 7 condition between adjacent paving sections.

V Ingview of the many changes and modifications that .may be made without departing from the principles underlying the invention reference should be made to'the -appendedclaims 'for anunderstandingflof the scope of the protection 'afiorded the invention.

, Having thus described my invention-,what

coated resin selected from; the group consisting of phenol aldehyde, resoreinolaldehyde, urea aldehyde,-

itated from a soluble state in' an aqueous acid medium the aldehyde I is selected from the group consisting of formaldehydeqand acetaldehyde .on the-Wet 1109s to coat the 'same, dewatering the coated rubber does of the flocculated latex, and drying said 7 rubber being selected from thegroupiconsisting of natural. rubbervand synthetic rubber, emulsion polymerizates 'ofmaterial selected from the group consisting of ibutadienes-lfi and mixtures of 'butadienes lfi with compounds which contain a Iclaim and fdesire-to'protect' by Letters Patent is: Y ';1.'Afree-flowing dried resin coated rubber. powder a the'particles'of Whichare 10'to 200 mesh size and are group and are copolymerizable" with butadienes-lfi.

6'. 'The'gmethod of making free iflowing resin coated rubber powder ofparticles of 10m 2001mesh'size from latex which' comprises first; flocculating the latex and then depositing anilinerfo i dehyde resin on the .wet does to coat the same, dewatering the' coated rubber floes of the flocculated latex, and drying, saidJubber. being selected from ,the group consisting of natural rubber and synthetic rubber emulsion polymerizates of material selected from the group consisting of butadienes-1,3 and mixtures of butadienes-1,3 with compounds which contain a CH =C group and are copolymerizable with butadienes-1,3.

7. The method of making free flowing resin coated rubber powder of particles of to 200 mesh size from latex which comprises first flocculating the latex and then depositing resin selected from the group consisting of phenol-aldehyde, resorcinal-aldehyde, urea-aldehyde, melamine aldehyde and aniline-aldehyde resins in which the aldehyde is selected from the group consisting of formaldehyde and acetaldehyde on the Wet rubber fiocs of the flocculated latex to coat the same, dewatering the coated flocs, and drying, said resin being precipitated from a soluble state in an aqueous acid medium in admixture with the flocculated rubber latex particles onto said flocculated rubber latex particles, said rubber being selected from the group consisting of natural rubber and synthetic rubber emulsion polymerizates of material selected from the group consisting of butadienes-1,3 and mixtures of butadienes-1,3 with compounds which contain a CH =C group and are copolymerizable With butadienes-l,3.

8. The method of making free flowing resin coated rubber powder of particles of 10 to 200 mesh size from latex which comprises first flocculating the latex and then depositing aniline-formaldehyde resin on the Wet rubber flocs of the flocculated latex to coat the same, dewatering the coated flocs, and drying, said resin being precipitated from a soluble state in an aqueous acid medium in admixture with the flocculated rubber latex particles onto said fiocculated rubber latex particles, said rubber being selected from the group consisting of natural rubbet and synthetic rubber emulsion polymerizates of material selected from the group consisting of butadienes-1,3 and mixtures of butadienes-1,3 with compounds which contain a CH =C group and are copolymerizable with butadienes-l,3.

9. A composition comprising a blend of bituminous material and a free flowing resin coated rubber powder as defined in claim 3, the rubber content of the blend being from 1 to 25 parts per parts of the bituminous material.

10. A composition comprising a blend of bituminous material and a free flowing resin coated rubber powder as defined in claim 4, the rubber content of the blend being from 1 to 25 parts per 100 parts of the bituminous material.

11. The method of uniformly dispersing rubber in bituminous material which comprises mixing with hot bituminous material a free flowing resin coated rubber powder prepared according to the method of claim 5.

12. The method of uniformly dispersing rubber in bituminous material which comprises mixing with hot bituminous material a free flowing resin coated rubber powder prepared according to the method of claim 6.

References Cited in the file of this patent UNITED STATES PATENTS 2,277,941 Almy Mar. 31, 1942 2,314,181 Winterkorn Mar. 16, 1943 2,610,158 Hall Sept. 9, 1952 2,700,655 Endres et a1 Jan. 25, 1955 2,845,397 Mills July 29, 1958 2,857,351 Carrol Oct. 21, 1958 FOREIGN PATENTS 381,587 Great Britain Oct. 7, 1932 OTHER REFERENCES Clinebell et al.: A Survey on the Use of Rubber in Bituminous Pavements, Rubber Age, volume 70, pub.

October 1951, page 70. 

7. THE METHOD OF MAKING FREE FLOWING RESIN COATED RUBBER POWDER OF PARTICULES OF 10 TO 200 MESH SIZE FROM LATEX WHICH COMPRISES FIRST FLOCCULATING THE LATEX THEN DEPOSITING RESIN SELECTED FROM THE GROUP CONSISTING OF PHENOL-ALDEHYDE, RESORCINAL-ALDEHYDE, UREA-ALDEHYDE, MELAMINE ALDEHYDE AND ANILINE-ALDEHYDE RESINS IN WHICH THE ALDEHYDE IS SELECTED FROM THE GROUP CONSISTING OF FORMALDEHYDE AND ACETALDEHYDE ON THE WET RUBBER FLOCES OF THE FLOCCULATED LATEX TO COAT THE SAME, DEWATERING THE COATED FLOCS, AND DRYING SAID RESIN BEING PRECIPATED FROM A SOLUBLE STATE IN AN AQUEOUS ACID MEDIUM IN ADMIXTURE WITH THE FLOCCULATED RUBBER LATEX PARTICULES ONTO SAID FLOCCULATED RUBBER LATEX PARTICULES, SAID RUBBER BEING SELECTED FROM THE GROUP CONSISTING OF NATURAL RUBBER AND SYNTHETIC TUBBER EMULSION POLYMERATES OF MATERIAL SELECTED FROM THE GROUP CONSISTING OF BUTADIENES-1,3 AND MIXTURES OF BUTADIENES-1,3 WITH COMPOUNDS WHICH CONTAINS A CH2=C< GROUP AND ARE COPOLYMERIZABLE WITH BUTADIENES-1,3. 